An example of a prior art tuned exhaust system embodied in an outboard motor is illustrated in the U.S. Miller Pat. No. 3,520,270, issued July 14, 1970. Attention is also directed to the U.S. Boerma Pat. No. 3,695,238, issued Oct. 3, 1972 and the U.S. Holtermann et al. Pat. No. 3,385,052, issued May 28, 1968.
Other patents of interest include the U.S. Kadenacy Pat. No. 2,102,559, issued Dec. 14, 1937; the U.S. Crowe Pat. No. 1,804,321, issued May 5, 1931; the U.S. Harralson et al. Pat. No. 3,967,446, issued July 6, 1976; and the U.S. Ehlan Pat. No. 3,842,599, issued Oct. 22, 1974.
Attention is further directed to the U.S. Draminsky Pat. No. 2,542,756, issued Feb. 20, 1951; the U.S. Nowak Pat. No. 3,462,947, issued Aug. 26, 1969; the U.S. Tenney Pat. No. 3,665,712, issued May 30, 1972; and the U.S. Tenney Pat. No. 3,703,937, issued Nov. 28, 1972.